Reflector (antenna)

About: Reflector (antenna) is a research topic. Over the lifetime, 28730 publications have been published within this topic receiving 212618 citations.

Device with resonant cavity for transmitting or receiving electromagnetic waves

Abstract: Aspects of the subject disclosure may include, a system for generating electromagnetic signals that resonate in a cavity having a plurality of reflectors resulting in resonating electromagnetic signals and combining the resonating electromagnetic signals to form an electromagnetic wave that traverses a reflector and couples onto a physical transmission medium. A plurality of fins is aligned radially outward from a surface of a physical transmission medium within a cavity between reflector. Other embodiments are disclosed.

Reflector antenna, especially for a communications satellite

Abstract: The invention provides a reflector antenna, especially for a communications satellite, having at least one fixed main reflector (102) with an essentially circular aperture. A fixed feed system (118) includes a horn radiator (108) with a rotationally symmetric radiation diagram and a fixed polarization direction. An auxiliary reflector may be arranged to be rotationally positionable around a main axis (E) and has a reflecting surface that is shaped as a partial surface of a nonrotationally symmetric ellipsoid with a low numerical eccentricity, which illuminates main reflector (102) elliptically with an ellipticity that is essentially constant regardless of the rotational position.

Digital holographic interferometry with CO2 lasers and diffuse illumination applied to large space reflectors metrology

Abstract: Digital holographic interferometry in the long-wave infrared domain has been developed by combining a CO2 laser and a microbolometer array The long wavelength allows large deformation measurements, which are of interest in the case of large space reflectors undergoing thermal changes when in orbit We review holography at such wavelengths and present some specific aspects related to this spectral range on our measurements For the design of our digital holographic interferometer, we studied the possibility of illuminating specular objects by a reflective diffuser We discuss the development of the interferometer and the results obtained on a representative space reflector, first in the laboratory and then during vacuum cryogenic test

A Reflector Antenna for Focusing Subnanosecond Pulses in the Near Field

Abstract: A prolate-spheroidal reflector antenna focusing subnanosecond pulsed electromagnetic radiation in the near field is studied. This antenna reflector is fed by a pair of balanced, conical-plate transmission lines and the radiated pulse consists of a prepulse, an impulse, and a postpulse. Whereas the prepulse amplitude decreases inversely with distance, the impulse is maximum near the geometric focus, and its power density distribution has a full-width at half-maximum (FWHM) width of 32 cm in the axial direction and 10 cm in the lateral direction.

Effects of reflector and crystal surface on the performance of a depth-encoding PET detector with dual-ended readout

Abstract: Purpose: Depth encoding detectors are required to improve the spatial resolution and spatial resolution uniformity of small animal positron emission tomography (PET) scanners, as well as dedicated breast and brain scanners. Depth of interaction (DOI) can be measured by using dual-ended readout of lutetium oxyorthosilicate (LSO) scintillator arrays with position-sensitive avalanche photodiodes. Inter-crystal reflectors and crystal surface treatments play important roles in determining the performance of dual-ended detectors. In this paper, the authors evaluated five LSO arrays made with three different intercrystal reflectors and with either polished or unpolished crystal surfaces. Methods: The crystal size in all arrays was 1.5 mm, which is typical of the detector size used in small animal and dedicated breast scanners. The LSO arrays were measured with dual-ended readout and were compared in terms of flood histogram, energy resolution, and DOI resolution performance. Results: The four arrays using enhanced specular reflector (ESR) and Toray reflector provided similar quality flood histograms and the array using Crystal Wrap reflector gave the worst flood histogram. The two arrays using ESR reflector provided the best energy resolution and the array using Crystal Wrap reflector yielded the worst energy resolution. All arrays except the polished ESR array provided good DOI resolution ranging from 1.9 mm to 2.9 mm. DOI resolution improved as the gradient in light collection efficiency with depth (GLCED) increased. The geometric mean energies were also calculated for these dual-ended readout detectors as an alternative to the conventional summed total energy. It was shown that the geometric mean energy is advantageous in that it provides more uniform photopeak amplitude at different depths for arrays with high GLCED, and is beneficial in event selection by allowing a fixed energy window independent of depth. A new method of DOI calculation that improved the linearity of DOI ratio vs depth and simplifies the DOI calibration procedure also was developed and tested. Conclusions: The results of these studies provide useful guidance in selecting the proper reflectors and crystal surface treatments when LSO arrays are used for high-resolution PET applications in small animal scanners or dedicated breast and brain scanners.